An NHS trust told by inspectors that it has "some way to go" before it is delivering an acceptable level of care has been identified by the government as the next one that may be placed in a form of special measures.

As the BMA warned that financial crises in a series of trusts should serve as a "wake up call", sources at the Department of Health said the Barking, Havering and Redbridge NHS Trust in north-east London could be placed in the regime designed to rescue failing trusts.

That follows the announcement on Monday by the health secretary, Andrew Lansley, that South London Healthcare Trust, which runs three hospitals in south-east London, is on course to become the first trust to be placed in the "unsustainable providers regime".

Ministers blamed the decision on a £150m deficit dating back to a £2.5bn deal, signed by the last government under the private finance initiative (PFI), to rebuild the Queen Elizabeth hospital in Woolwich and the Princess Royal University hospital in Orpington.

The impact of PFI payments will be highlighted on Wednesday when the Care Quality Commission (CQC) watchdog warns that the Barking, Havering and Redbridge trust is struggling to meet its financial commitments. Unlike the South London trust, whose treatment record is relatively strong, the north-east London body is also told it is failing to deliver proper standards of care.

The A&E department at Queen's hospital, Romford, which is part of the trust, is still causing concern after a history of poor performance at the trust, including in maternity services, complaints handling and leadership, according to the commission. Although some improvements have been made after more than two years of CQC concern, the trust still has "some way to go", according to the watchdog.

The trust, which is responsible for Queen's and King George hospital, Ilford, has changed operating structures in recent months but the CQC says more needs to be done on staffing and "it is too early to say in many cases whether permanent improvements have been achieved."

The Barking trust has to find nearly £50m this year on its PFI deal agreed in January 2004, but is one of seven, including South London NHS trust now being allowed to go bust, that were originally offered grants from a £1.5bn Department of Health pot designed to help those in difficulty meet their PFI costs without cutting services to patients. But they have to meet strict conditions to get the money.

The CQC says of the Queen's A&E department: "Delays in admission due to 'blockages' in the system and lack of beds throughout the hospital cause backlog of patients within the department. The hospital also continues in their struggle to recruit middle grade doctors and reliance is placed on using doctors from locum agencies. This reliance increases the risk and reduces the level of senior medical cover in the department. Overall this is exposing patients to unnecessary and increased risk of poor care."

Matthew Trainer, deputy director of CQC in London, said: "The direction of travel at the trust is encouraging but – as they acknowledge – they still have some way to go before they are consistently delivering the quality of care that local people are entitled to expect."

The trust's chief executive, Averil Dongworth, said: "Making changes that can be sustained takes time, but I'm pleased that some of the improvements we have been making, particularly in maternity, are already getting positive feedback. We've made good progress, but I agree with the CQC that we still have some way to go in making improvements that can be sustained for the future."

It is understood that Lansley feels the trust is working hard to resolve its problems and does not need to be placed in "unsustainable providers regime" at the moment. But one source said: "The trust is not in the same place as the South London Healthcare Trust but it could get there if it does not get its act together."

Dr Hamish Meldrum, the BMA's chairman of council, said the decision to place the South London Healthcare Trust into special measures highlighted the rigidity in the NHS. "There isn't any flexibility or financial leeway in the system," Meldrum said. "This really is a wake up call."